CNN's aviation correspondent Richard Quest once visited MH370's 1st Officer Fariq Ab Hamid in a Malaysia Airlines cockpit, when he was training. Quest watched him land the plane under supervision of a senior pilot in February.

The captain described Fariq's landing as textbook perfect.

Fariq joined Malaysia Airlines in 2007. He has 2,763 flying hours behind him and was transitioning to the Boeing 777-200 after finishing training in a flight simulator.

As with Zaharie, not much is known to the public about Fariq. But Quest was not the only guest who had joined him in the cockpit.

Does Roos' story open up the possibility that a third or fourth person could have joined Zaharie and Fariq in the cockpit?

Like the exact whereabouts of Flight 370, that's yet unknown. But investigators believe that somebody must have done something.

Not long after the flight took off from Kuala Lumpur communications systems were disabled, the plane's transponder was turned off, Malaysian Prime Minister Najib Razak said Saturday.

That last device is situated between the pilots and can be shut off with a twist of the wrist. For a pilot to turn it off would seem reckless because the information it transmits gives the plane vital protection. It helps people on the ground locate the plane.

Someone would have to know how to do it and also know the plane would lose that protection.

Then someone in the cockpit said good night.

And the apparent lack of visibility on radar? "Airline pilots are not trained for radar avoidance," said aviation expert Keith Wolzinger, a former 777 pilot. They like to stay on the radar, because -- again -- it protects their plane.

Only military pilots, he said, are usually keen on avoiding radar.

The father of a passenger on the missing plane is hoping for an outcome that would sound shocking under normal circumstances.

"I hope the plane was hijacked, because then, at least, there is hope," Li from Hebei Province said. He did not give his full name.

Li is waiting at a Beijing hotel with dozens of other passengers' family members awaiting word on the fate of their loved ones.

"But if the worst happened then I will have no meaning in my life. This is my only son," Li said.